# Engineers Corner > Mechanical Engineering hover force calculation

## daemgmt

Hello team,

This is my problem, given an object that weighs a 1000 pounds and hovers in one spot on a nine inch cushion of air, how would you calculate the minimum force needed to move the object forward, backward, side to side and or in a circle? Given, that there will be an unknown variable force resistance of matter.  Also, air force can only be used.

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## Stercus

Just to move the 1000lb mass, in theory, you're looking at the starting or static frictional force, not the dynamic friction force - usually in fluid mechanics you would use the latter to work out the drag to be overcome at a certain fluid velocity. For a cushion of air, this wouldn't be realistic - the forces involved in keeping the thing hovering on the cushion of air would be significantly larger and would involve a fluid flow already - there would have been no 'starting friction' to overcome.

If you want a proper answer you'll have to look a lot further, as the frictional forces in a fluid cushion get complicated - and you'd be better off with an empirical measurement. If you're after an easy answer, throw in Newton's Second Law - F x dt = m x dv. So for any force applied for a given time, you'll get an acceleration - works in any direction too, even in a circle!

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